while True:
    try:
        ncows, ncars, nshow = map(int, input().strip().split(' '));
        ans = (ncows/(ncows+ncars))*(ncars/(ncows+ncars-nshow-1)) \
                + (ncars/(ncows+ncars))*((ncars-1)/(ncows+ncars-nshow-1))
        print("{:.5f}".format(ans))
    except:
        break;
